A magnetic storage device that stores therein information by using magnetization reversal by a magnetic field of an electric current is manufactured by using a semiconductor wafer in which various layers are laminated and etched in desired patterns. One of the layers of the magnetic storage device is a Pt—Mn layer containing Pt as a magnetic material. However, Pt is known as a material that is hardly etched.
As for an etching method for the Pt—Mn layer, there is known, a method for physically etching the Pt—Mn layer by ion milling, e.g., by sputtering using Ar positive ions of high energy. However, in the etching method of ion milling, positive ions are incident on a mask layer and a Pt—Mn layer with high energy. Therefore, it is difficult to obtain selectivity between the mask layer and the Pt—Mn layer. Further, the pattern shape of the mask layer is collapsed at an initial stage, and thus, a hole or a trench obtained by etching has a tapered shape (see, e.g., “Dry etching of high-k materials” of Ono Koichi, Takahashi Kazuo, and Erikuchi Koji: Journal of Plasma Fusion Research, Vol. 85, No. 4 (2009), pp. 185-192, issued in January 2009)
Furthermore, there has been proposed a method for chemically etching the Pt—Mn layer by an etching gas containing a highly reduced halogen gas of high reducibility (see, e.g., Japanese Patent Application Publication No. 2006-60172). Moreover, there is suggested a method for performing dry etching on a Pt layer by using a gaseous mixture of a halogen gas and CO (see, e.g., Japanese Patent Application Publication No. H10-68094).
Since, however, the halogen gas generates strong acids, corrosion of components of an etching apparatus is accelerated. Further, it is difficult to obtain a vertical sidewall, and the hole or the trench becomes tapered in shape.